Heat regenerator particulary a hot blast stove for a blast furnace plant

ABSTRACT

In a heat regenerator, in particular a hot blast stove for a blast furnace plant, which comprises an upstanding masonry structure closed on top by a dome of refractory bricks, the dome passes into the vertical masonry structure below it by means of a continuous series of elements which are pivotally connected both to the stove structures below it close to the upper edge of the vertical masonry structure and to the lower edge of the dome.

O Umted States Patent [191 [111 3,713,632 Beenhakker et al. I 1 Jan. 30,1973 [541 HEAT REGENERATOR, PARTICULARY {56] References Cited A HOTBLAST STOVE FOR A BLAST FURNACE PLANT UNITED STATES PATENTS [75]Inventors: Albertus Hendrik Beenhakker, Sant- 33341880 8/1967 Hishida"263/19 R Jmb Oudmpi bmh FOREIGN PATENTS OR APPLICATIONS of NetherlandsAssignee: xomnklyke Nederlandsche 879,741 I0/l96l Great BrItaIn ..263/l9R Hoogovens En Staaliabrieken N.V. Primary Examiner Edward G Favors [22]Filed: March 2, 1971 Attorney-Hall & Houghton [21] Appl. No.: 120,267[57] ABSTRACT In a heat regenerator, in particular a hot blast stove[30] Forelgn Apphcamn Pnomy Data for a blast furnace plant, whichcomprises an upstand- March 3, l970 Netherlands ..7003023 ing masonrystructure closed on top by a dome of l V n I refractory bricks, the domepasses into the vertical 52 us. Cl. ..263/19 R masonry Structure belowit y means of a continuous 51 Int. Cl ..F23l 15/02 Series of elementswhich are Pivotally connected both [58] Field of Search ..263/19, 51 tothe Steve Structures below it close to the PP edge of the verticalmasonry structure and to the lower edge of the dome.

6 Claims, 4 Drawing Figures 12 5 R 1 I 13 i 11.

PATENTEUJAN 30 I975 SHEET 10F 2 INVENTORS AMER 705 H Et'E Yfl YAIKER 5Z160 F517 um BY W 1 ATTORNEY PATENTEUJAN 30 1973 3.713.632 SHEET 2 BF 2HEAT REGENERATOR, PARTICULARY A HOT BLAST STOVE FOR A BLAST FURNACEPLANT This invention relates to a heat regenerator, in particular to ahot blast stove for a blast furnace plant, comprising a verticalstructure of masonry, closed at the top by a dome of refractory bricks.

In particular in the blast furnace art there is an ever increasing needof air preheaters, so-called hot blast stoves, sufficing higherrequirements of operation. As the blast furnaces are in these daysincreasing in dimensions and capacity and have to produce pig iron at ahigher efficiency, the hot blast stoves for such blast furnaces have tosupply ever increasing quantities of air at higher temperatures. Thisentrains that the refractory domes of such stoves also have to havelarger dimensions and that these domes and the structure of theconnection thereof to the remainder of the stove have to be able towithstand higher temperatures.

In this respect it may be remarked that the domes should be able towithstand temperatures up to about 1800 C during operation, and alsohave to withstand considerable temperature variations in short timeintervals during heating up and cooling down.

It has appeared that the large and non-uniformly distributed thermaldilatations of the dome cause considerable difficulties, particularly inthe zone of the connection between the dome and the remainder of thestructure. The differences in dimensions occurring between the loweredges of the dome and the upper edge of the vertical masonry structureof the stove below the dome may amount to about 1 percent of thedimensions of this part of the stove. This gives rise to the formationof serious vertically extending cracks or fissures in the dome.

Although as a rule such cracks were already known for smaller airpreheaters, heated to lower tempera tures, they did not cause seriousproblems in such smaller stoves. For larger brick domes, however, wherestability is already an important problem without such effects, theoccurence of cracks will more easily have fatal results.

Particularly if the temperature of the dome will rise up to about l600C, the danger of collapse of the dome will become very great.

The above is true both for domes of hot blast stoves with an internalburner stack as for stoves with an external burner stack.

In view of the above the invention aims at providing such a structure ofthe dome of such stoves that such cracks cannot or can hardly occur andeven if they occur, will not do harm. In view thereof a structureaccording to the invention'as given above is characterized in that thedome passes into the vertical masonry structure below it by means of acontinuous series of elements which are pivotally connected both to thestove structure below it close to the upper edge of the vertical masonrystructure and to the lower edge of the dome.

Where in this specification reference is made to structures in which thedome passes into the vertical masonry structure, structures are alsodeemed included in which this connection is not realized in contact withthe upper edge of the vertical masonry of the stove itself below thedome, but in contact with an annular element providedall around thisupper edge for giving a support of the dome not upon but outside thevertical masonry structure below the dome.

Preferably according to the invention the said pivoting elements havethe shape of columns being more or less in line with the adjacent partof the dome for each column, the pivots being formed by supportingsurfaces having the shape of faces being parts of circular cylinders onthe one hand at the upper ends of the columns and the lower edge of thedome and on the other hand at the upper edge of the vertical masonrystructure.

It is remarked that such a possibility of movement of the columns bypivoting at both ends has clear and considerable advantages over asupport of the dome on balls or on rollers at the upper edge of thevertical masonry structure.

in this respect it is remarked that such pivotable columns, also bytheir greater length, can take up considerable differences in dilatationmuch more easily than rollers. More important, however, is that therollers should be cooled locally in order to avoid their being sinteredto one mass with the surrounding brick structures. Moreover, as a resultof such cooling of the rollers, the adjacent part of the dome willbecome too cold. This would again cause serious cracks in the dome as aresult of the discontinuity in the dilatation characteristics of therefractory material of the dome in the temperature region at which thisdome would have to operate.

As the dome according to the invention will have obtained a freepossibility of movement with respect to the remainder of the structureand also as the dome is allowed to obtain a substantially constanttemperature, it is thereby made possible to build up this dome entirelyfrom silicon bricks.

in other structure it has appeared that the unavoidable considerabledifferences in temperature of the dome make it impossible to choose thismaterial, which for other reasons is preferable. This would be due tothe fact that there are considerably great and sudden temperaturedilatations occuring in silicon bricks when passing theirrecrystallization temperature.

It has appeared that it is possible for the columns to take up the sametemperature as the dome without any harm. Even if this would cause someslight sintering in the pivoting connections, this is easily loosenedagain in practice without any harm to the structure. This is a result ofthe bending moment which is exerted on the pivots and which by thelarger lever arms of such moments is much greater than the bendingmoment which would occur in rollers as indicated above.

It is remarked that in general in refractory structures, and in hotblast stoves in particular, there is the general tendency to decreasethermal stresses by applying a more heavy and more rigid structure. Themany uncertainties which occur in refractory structures which are highlyloaded mechanically, particularly during heating up and cooling'periods,are a ground for the fact that the experts did usually not dare to buildless heavy and less rigid structures with more freedom of movement. Thusthe structure according to the invention with a dome supported allaround through many pivots is a structure which is not at all obviousfor the expert, which is of a daring nature technically and which isquite surprising in its effects.

In order to restrict to a minimum a free movability of the dome on theremainder of the structure other than for taking up differences inthermal expansion it is according to the invention preferable to givethe columns in the direction of their mutual row or series (so in theperipheral direction of the stove) a dimension which for each of them is1 to 2 times larger than the dimension of the columns in their thicknessdirection (about radially of the stove). Thereby each column issubstantially only allowed to rotate about one axis and it is thusrestricted in its possibilities of movement by all other columns beingpivotable about axes having different directions. This avoids the dometo move around its own axis.

It is known as such, e.g., for steel bridges, to use very short pivotingcolumns at the supports thereof. However, such supports only serve totake up displacements in one direction and of much smaller size.Moreover, such columns are in those cases as a rule formed as parts ofrollers, so that the possibility of movement is in fact only a rollingmovement and no pivoting movement.

In further contradistinction to this known structure it is according tothe invention preferable to provide the pivots at both ends of thecolumns with convex upper surfaces, cooperating with concave lowersurfaces.

Although this structure is not very obvious, it has the advantage thatthe columns, which are relatively long with respect to the dimensions ofthe pivots, have less possibility to pivot out of the space between thedome and the remainder of the structure.

In order to make the movement of the columns better predictable, butalso for other reasons of a nature important in the building offurnaces, care should be taken that the columns at their lower ends canonly move as slightly as possible in a radially outer and innerdirection. This also avoids that the slots between the columns wouldbecome too wide.

This object is according to the invention obtainable if the upper end ofthe vertical masonry structure below the dome is provided at least inpart with vertically extending expansion joints, said upper end beingbacked up by means which leave the shape thereof substantally unalteredwith considerable varying temperatures of the vertical masonrystructure. Such means could, e.g., have the shape of an annular elementaround the upper edge of the vertical masonry structure, such an annularelement being known as such, the dome passing into said annular elementthrough the columns. The means for backing up the said upper end as arule consist of an obvious steel structure, provided in a region wherethe temperature is always sufficiently low.

It has already been remarked that the structure according to theinvention could be applied for air preheaters such as hot blast stovesboth with interior and also with exterior burner stack. When applyingthe invention to an interior burner stack structure it appears to beadvantageous to take into account the manner of supporting the domeaccording to the invention in choosing the shape of the dome.

In this respect it has appeared that in such a new structure throughwhich the side wall of the stove passes into the dome for a hot blaststove with a main body being a circular cylinder and with an interiorburner stack, this dome should preferably have the shape of a segment ofa sphere which in a section along a meridian covers an arc of to thissegment of a sphere merging into a surface of revolution which in ameridian section consists of two circular arcs (one on each side) whichhave a radius which is 3 to 4 times larger than the radius of thesegment of a sphere.

The invention will now further be explained with reference to theenclosed drawings giving by way of example only a preferred embodimentof the invention.

FIG. 1 gives a diagrammatic vertical section through a hot blast stoveaccording to the invention;

FIG. 2 gives detail II in FIG. 1 on a larger scale;

FIG. 3 gives detail III of FIG. 1 on a larger scale;

FIG. 4 gives the same detail as detail II of FIG. I (FIG.2), but of adifferent embodiment.

In FIG. 1 reference numeral 1 indicates a vertical cylindricalrefractory brick wall of a hot blast stove. This stove as shown has aninterior burner stack 2, which is separated from the space 4 by aseparating wall 3. In space 4 there is a pile of refractory bricksadapted to take up heat from hot gases and to give off heat to air to bepreheated and such a pile of bricks is not shown but is quite usual andknown as such.

At the upper end the structure is closed by dome 5 of refractorymaterial symmetrical to a vertical central axis. Around this structurethere is a steel jacket as is usual, which is not shown.

A supply duct for air 6 and a supply duct for combustible gas 7 openinto a burner 8 as usual. A grid 9 supports the said pile of bricks inspace 4. There is an opening 10 below this grid for allowing gases toescape after giving off their heat to the pile of bricks and for coldair to enter the stove for being heated. An opening 11 in wall 1 in theburner stack allows the heated air to leave the preheater.

The dome consists of a part 12 having the shape of a segment of sphere,passing into the dome part I3 which is part of a surface of revolution.The radius of the spherical part 12 is about 35 percent of the diameterof the outer wall 1 and in a section through a meridian covers an arc of104. The dome part 13 merges without a sharp transition into part 12 andin a meridian section part 13 has a radius which is about 3.7 times theradius of segment 12. The transition zone of dome part 12 into dome part13 has been shown by a dotted line in FIGS. 1 and 2.

With the aid of columns 14 the dome 5 is supported pivotally on theouter wall 1'. However, it is also possible to support the dome on anannular element not shown, which is connected to the surrounding steeljacket around the outside of the upper edge of outer wall 1, e .g., in amanner which is known as such.

In FIGS. 2 and 3 this support has been shown in more detail, FIG. 2showing the support in a vertical section according to detail II in FIG.I and according to the line II-Il in FIG. 3.

FIG. 3 shows detail III of FIG. I in a view from the interior radiallyoutwards.

The lower edge of dome part 13 is rounded according to a semi-circularshape. The semi-cylinder thus formed fits into semi-cylindricalconcavities in the upper ends of columns 14. To obtain such straightparts it is possible to have the bricks in the lower part of the domepart 13 follow such a configuration that this lower edge only consistsof a number of straight parts.

In a similar manner the semi-circularly rounded lower edges of thecolumns 14 fit into semi-cylindrical concavities in the top edge of thevertical brick wall 1 of the stove.

The top part of the vertical masonry structure of wall 1 is providedwith vertical expansion joints or slots 17, closing when the stovereaches the operating temperature, or at least closing partly, servingto avoid high compression stresses in the bricks and high tensilestresses in the steel outer lining when the stove is at operatingtemperature.

The columns 14 have the same thickness as dome part 13, e.g., somewhatmore than 30 cm.

The width of the columns 14 is preferably about 60 cm.

In FIG. 4 detail II of FlG.l is shown for a different embodiment, inwhich the dome is not directly supported by the vertical masonry of thestove. A steel shell 18 surrounds this masonry and merges upwardly intoan annular part 23 flaring outwardly and merging itself upwardly intothe steel outer structure of the dome. Annular part 23 is supported by arow of steel brackets or struts 24 around the outside of the stove.

The vertical masonry of the stove in the top part is here shown toconsist of three layers 19, 20 and 21, having vertical dilatation joints17 in planes through the axis of the regenerator similar to those inFIGS. 2 and 3.

The annular part 23 with brackets 24 are positioned in a relatively coolarea, so that they do not expand considerably when the stove is heated.Thus also the diameter of the vertical masonry 19, 20 and 21 remainssubstantially unaltered. The expansion of this masonry by heating isthus almost entirely taken up by the joints l7 dimensioned so as to beentirely closed in operating conditions of the highest temperature.

The annular part 23 supports pivoting blocks 25, into which columns 26fit in a pivoting manner. These refractory columns are essentially ofthe same shape and kind of material as the columns 14 in the previousembodiment. They support the dome by pivoting connection with the loweredge of the inner dome 27 of refractory bricks. Outside this dome 27 asecond refractory brick layer 28 is present, in contact with the steelouter lining of the dome.

The vertical masonry wall could, instead thereof, be flared outwardly tooverly the annular part 23, in which case the pivoting blocks will bepositioned on top of this part of the vertical masonry wall of theregenerator. Many details of the regenerator, which are not importantfor understanding the invention, have not been shown and described. So,it will be clear that there is a steel dome over the refractory dome 5and a porous, somewhat elastic heat-insulating layer between thesedomes, as is usual. Such details will be clear to the expert.

What we claim is:

l. A heat regenerator, in particular a hot bast stove for a blastfurnace plant, comprising an upstanding masonry structure, closed on topby a dome of refractory bricks,

characterizedinthatthe domepassesinto the vertical masonry structurebelow it by means of a continuous series of elements which are pivotallyconnected both to the stove structures below it close to the upper edgeof the vertical masonry structure and to the lower edge of the dome.

2. A heat regenerator according to claim 1,

characterizedinthatthesaidpivotingelements have the shape of columnsbeing more or less in line with the adjacent part of the dome for eachcolumn, the pivots being formed by supporting surfaces having the shapeof faces being parts of circular cylinders on the one hand at the upperends of the columns and the lower edge of the dome and on the other handat the upper edge of the vertical masonry structure or other structurebelow such columns.

3. A heat regenerator according to claim 2,

characterizedinthatthecolumnsinthe direction of their mutual row orseries (so in the peripheral direction of the stove) have a dimensionwhich for each of them is l to 2 times larger than the dimension of thecolumns in their thickness direction (about radially of the stove).

4. A heat regenerator according to claim 2,

c haracterizedinthatthe pivotsatbothendsof the columns have convex uppersurfaces cooperating with concave lower surfaces.

5. A heatregenerator according to claim 1,

characterizedinthattheupperendofthevertical masonry structure below thedome is provided at least in part with vertically extending expansionjoints, said upper end being backed up by means which leave the shapethereof substantially unaltered with considerably varying temperaturesof the vertical masonry structure.

6. A heat regenerator according to claim 1, having the shape of acylindrical hot blast stove with a circular cross-section and interiorburner stack,

characterizedinthatthetoppartofthedome has the shape of a segment of asphere which in a section along a meridian covers an arc of to 1 l0,this segment of a sphere merging into a surface of revolution which in ameridian section consists of two circular arcs (one on each side) whichhave a radiuswhich is 3 to 4 times larger than the radius of the segmentofa sphere.

i i i it

1. A heat regenerator, in particular a hot bast stove for a blastfurnace plant, comprising an upstanding masonry structure, closed on topby a dome of refractory bricks, c h a r a c t e r i z e d i n that thedome passes into the vertical masonry structure below it by means of acontinuous series of elements which are pivotally connected both to thestove structures below it close to the upper edge of the verticalmasonry structure and to the lower edge of the dome.
 1. A heatregenerator, in particular a hot bast stove for a blast furnace plant,comprising an upstanding masonry structure, closed on top by a dome ofrefractory bricks, c h a r a c t e r i z e d i n that the dome passesinto the vertical masonry structure below it by means of a continuousseries of elements which are pivotally connected both to the stovestructures below it close to the upper edge of the vertical masonrystructure and to the lower edge of the dome.
 2. A heat regeneratoraccording to claim 1, c h a r a c t e r i z e d i n that the saidpivoting elements have the shape of columns being more or less in linewith the adjacent part of the dome for each column, the pivots beingformed by supporting surfaces having the shape of faces being parts ofcircular cylinders on the one hand at the upper ends of the columns andthe lower edge of the dome and on the other hand at the upper edge ofthe vertical masonry structure or other structure below such columns. 3.A heat regenerator according to claim 2, c h a r a c t e r i z e d i nthat the columns in the direction of their mutual row or series (so inthe peripheral direction of the stove) have a dimension which for eachof them is 1 to 2 times larger than the dimension of the columns intheir thickness direction (about radially of the stove).
 4. A heatregenerator according to claim 2, c h a r a c t e r i z e d i n that thepivots at both ends of the columns have convex upper surfacescooperating with concave lower surfaces.
 5. A heat regenerator accordingto claim 1, c h a r a c t e r i z e d i n that the upper end of thevertical masonry structure below the dome is provided at least in partwith vertically extending expansion joints, said upper end being backedup by means which leave the shape thereof substantially unaltered withconsiderably varying temperatures of the vertical masonry structure.